Method and apparatus for measuring the flatness of sheet material wherein a scale is superimposed upon the sheet

ABSTRACT

A method of measuring the flatness of rigid, moving sheet material, for example sheet metal as it is produced in a rolling mill, comprising supporting the sheet on two substantially horizontal supports spaced apart in the direction of movement of the sheet material, arranging above or below the moving sheet material a scale graduated to indicate the degree of flatness of the sheet material, preferably in terms of mon numbers and producing an image of the scale graduations by reflection in the upwardly facing or downwardly facing surface of the sheet material in a region between said supports. Apparatus for performing the method is also described.

Haines tes tent [54] METHOD AND APPARATUS FOR MEASURING THE FLATNESS 0F SHEET MATERiAlL WHEREHN A SCALE 1S SUPERIMPOSED UPON THE SHEET inventor:

Assignee:

Filed:

Appl. No.:

Derrick J. Haines, Swansea, Wales University College of Swansea Aug. 3, 1970 Foreign Application Priority Data 33/147 L, 147 E, 125 A, 125 R, 46R

[ lFeb. 1, 1972 56] References Cited UNITED STATES PATENTS 1,183,139 5/1916 Taub ..33/l25 R Primary Examiner-Ronald L. Wibert Assistant Examiner-Orville B, Chew, ll Att0rney-Michael S. Striker A method of measuring the flatness of rigid, moving sheet material, for example sheet metal as it is produced in a rolling mill, comprising supporting the sheet on two substantially horizontal supports spaced apart in the direction of movement of the sheet material, arranging above or below the moving sheet material a scale graduated to indicate the degree of flatness of the sheet material, preferably in terms of mon numbers and producing an image of the scale graduations by reflection in the upwardly facing or downwardly facing surface of the sheet material in a region between said supports. Apparatus for performing the method is also described.

ABSTRACT 8 Claims, 2 Drawing Figures wow 0 rot 1e CElfLKE IO rovle EDGE PATENTED FEB 1 I97? SHEET 1 OF 2 mmvow OSOL .7 J d 0 OH mmqswMose O OH m r L DO 1.

lrwen or 0:12am: 102mm l w/H A ltorney PAIENTEDFEB 1m SHEET 2 BF 2 Attorney METHOD AND APPARATUS FOR MEASURING THE FLATNESS OE SHEET MATERIAL WHEREIN A SCALE KS SUPEIRHMPOSED UPON THE SHEET This invention relates to measurement of the flatness of rigid, moving sheet material. In particular, but not exclusively, the invention relates to a method of, and means for, measuring the flatness of sheet metal strip as it is being manufactured in a rolling mill.

in the manufacture of sheet metal strip in a rolling mill it is highly desirable that the rolled product should be as flat as possible, since flat sheet material is of considerably greater value than buckled sheet material.

The main reason for sheet metal strip becoming buckled transversely of the rolling direction during manufacture is that the strip is subjected to different degrees of longitudinal extension at locations across its width during the rolling process. The most usual cause of this is local variations in the widths of the rolling gaps of the mill.

If a buckled rectangular sheet of metal produced in a rolling mill is cut into a plurality of narrow, parallel-sided strips, with the axes of the strips parallel to the rolling direction, it will be found that the individual strips, which had the same length when joined together in the sheet, have slightly different lengths. The difference in length of two strips is a measure of the degree of buckling of the sheet, which is usually expressed as the mon number of the sheet. A mon number of unity represents a difference in free length of one strip relative to another of one part in Thus, if a first of the above-mentioned strips has a length of L and a second strip has a length of L( l+l/l0,000), then the second strip is said to be 1 mon longer than the first. If the second strip is cut from the center of the original rectangular sheet and the first strip from an edge, then the sheet is said to have a long center value of 1 mon. If, on the other hand, the second strip is cut from the edge of the sheet and the first strip from the center, then the sheet is said to have a long edge value of 1 mon.

In order to produce high-grade sheet metal strip it is desirable to monitor the flatness of the strip as the strip is being produced. If the strip shows a tendency to depart from a predetermined standard of flatness, steps can then be taken to correct the tendency.

One object of the present invention is to provide a method of measuring the flatness of rigid, moving sheet material.

According to the invention a method of measuring the flatness of rigid, moving sheet material comprises supporting the sheet on two substantially horizontal supports spaced apart in the direction of movement of the sheet material, arranging above or below the moving sheet material a scale graduated to indicate the degree of flatness of the sheet material, and producing an image of the scale graduations by reflection in the upwardly facing or downwardly facing surface of the sheet material in a region between said supports.

By observing where the edges of the moving sheet material appear to intersect the image of the scale graduations, it is possible to obtain a direct reading of the flatness of the sheet material.

Preferably, the scale is graduated directly in mon numbers and is graduated to indicate sheet material with a long center condition and sheet material with a long edge condition.

The method of the invention may be used not only to provide a measurement of the flatness of sheet material as it is being produced, but also as a quantitative check ofthe flatness of sheet material, for example sheet metal strip, being fed into a manufacturing plant. The flatness of sheet material is a frequent source of friction between the producer of the material and the user thereof due to the absence of any relia ble device for checking material flatness after manufacture by the producer and before use by the user.

According to a further aspect of the invention, a method of measuring the flatness of sheet metal strip as it is being produced in a rolling mill, comprises supporting the moving strip on a pair of spaced apart supporting rollers having their axes of rotation substantially horizontal and disposed substantially at right angles to the direction of movement of the strip, arranging above or below the moving strip a scale graduated to indicate the degree of flatness of the strip, the scale preferably being graduated to indicate mon numbers of the strip, and producing an image of the scale graduations by reflection in the upwardly facing or downwardly facing surface of the strip in a region between said supporting rollers.

In this specification the term supporting roller" is used to define any roller forming part of, or associated with, a rolling mill which serves to assist in the movement of the strip or per forms a tensioning or guiding function on the strip. Included within the term supporting roller, therefore, are pinch rolls, guide rolls, nip rolls, work rolls, levelling rolls and roller leveller rolls.

in the case of manufacturing sheet metal strip, by observing where the edges of the moving strip appear to intersect the image of the scale, the rolling mill operator is given a quantita tive measure of the flatness of the strip as it is being produced so that (a) appropriate remedial action can be taken, and/or (b) detailed records can be made of strip quality while the strip is being produced.

A simple explanation of the theory on which the method of the invention is based will now be given. When a strip of sheet material is travelling over spacedapart horizontal supports it will hang in a curve between the supports, which curve, to a close approximation, is a catenary. If the strip is perfectly flat, in its free state, the catenary will have the same shape across the strip from one longitudinal edge of the strip to the other. If, however, the strip is not perfectly flat, due to variations in longitudinal tension across the strip, differences in the free longitudinal length of the strip in transversely spaced-apart zones, and tension in the strip at right angles to its longitudinal direction, then the strip will hang in a curve which is made up of a spectrum of catenaries. If the strip has a long center condition, then it will hang in a deeper catenary at the center than at its edges. If on the other hand, the strip has a long edge condition, it will hang in a shallower catenary at the center than at its edges. Consequently, in an unsupported part of the strip, between the supports, a strip with a long center condition will have a downwardly bowed transverse section, whereas a strip with a long edge condition will have an upwardly bowed transverse section. Thus the upwardly facing surface of a strip with a long center condition or the downwardly facing surface of a strip with a long edge condition, will act as a concave mirror and the upwardly facing surface of a strip with a long edge condition, or the downwardly facing surface of a strip with a long center condition, will act as a convex mirror.

it will therefore be appreciated that if a substantially horizontal, rectilinear, graduated scale is placed above or below the moving strip, which scale has a length greater than the width of the strip and is disposed at right angles to the longitudinal direction of the strip, then the number of scale graduations that can be seen in the image of the scale formed by reflection in the surface of the strip will vary according to whether the strip is flat, has a long center condition, or has a long edge condition. It is a matter of simple geometrical and optical calculations to determine the spacing apart of the scale graduations and the position of the scale above or below the strip in order that the mon number of the strip can be read directly by observing the image of the scale.

According to a further aspect of the invention, means for measuring the flatness of sheet metal :strip moving between two substantially horizontally disposed supporting rollers as it is being produced in a rolling mill, comprises a substantially rectilinear scale graduated in mon numbers for the strip, and a frame adapted to support the scale substantially horizontally at a predetermined distance above or below the moving strip in a direction substantially at right angles to the direction of movement of the strip,

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawing, in which:

HO 1 is a schematic perspective, view of part of a rolling mill, and

FIG. 2 is a schematic perspective view of a modified embodiment of part of the rolling mill shown partly in FIG. I, a portion of this Figure being shown broken away.

In FIG. I, the numerals 1 and 2 designate two spaced-apart supporting rollers in a rolling mill across which a strip 3 of sheet metal is travelling in the direction of the arrow A. The axes of the rollers l and 2 are substantially horizontal and disposed at right angles to the rolling direction.

A rectilinear scale 4 is supported above the strip 3 by a frame 5. The scale 4 is horizontally disposed and at right angles to the direction of travel of the strip. THe center of the scale, marked by the line 6, is arranged directly above the center of the strip. On each side of the center line 6 the scale 4 is graduated in terms of mon numbers, the two zero positions of the scale being separated by a distance x equal to the projected width of the strip 3.

The numeral 7 designates the image of the scale 4 seen in the upwardly facing surface of the strip 3. The scale readings where the edges 8, 9 of the strip appear to intersect the image 7 give the mon number of the strip. In the case shown, the strip 3 is bowed downwardly in transverse section. In other words it has a long center condition, and the image 7 shows a mon number of approximately 8.

If instead of a long center condition, the strip 3 had a long edge condition, the image 7 would show more of the scale 4 and the edges 8, 9 of the strip would appear to intersect the image in the long edge part of the scale.

To facilitate reading of the image 7, the markings on the scale 4 are mirror image representations, so that the markings observed on the image are the right way round.

Any necessary lighting may be arranged in the vicinity of the scale 4 to illuminate the latter and any suitable optical system (not shown) may be arranged so that the image 7 can be observed by an operator at a remote point, for example at a control desk for the rolling mill.

In another embodiment of apparatus for carrying out the method according to the invention, the simple rectilinear scale 4 shown in FIG. 1 may be replaced by a cylindrical or prismoidal drum having its longitudinal axis disposed horizontally. Such a scale is shown in FIG. 2 in which it is generally designated by the reference numeral 14. The scale 14 comprises a cylindrical drum 15, the scale graduations consisting of a row of holes 16 formed through the drum along a generatrix of the drum. One or more electric lights 17 are arranged inside the drum. Adjacent to each graduation hole 16 the drum has holes 18 formed therethrough in the pattern ofa number, which preferably is the mon number corresponding to that particular graduation hole. In this way the scale and a light source therefor are combined in a single unit. The drum type scale shown in FIG. 2 can be provided with further rows of scale graduation holes 16a, 16b, etc., each row being disposed along a different generatrix of the drum. In this case the drum is rotatably mounted on a shaft 19, which may serve as a support for the light source 17. By indexing the drum on the shaft 19 to the appropriate angular position, the correct scale, having regard to the width of the strip of material under observation.

It will, of course, be appreciated that, in either of the embodiments described above, the scale may be arranged below the strip 3 instead of above. In this case the long edge part of the scale would be in the center zone of the scale and the long center" part would be at the ends of the scale.

Although the above description is concerned with the measurement of the overall flatness of sheet material, it will be appreciated that the method and means according to the invention may be used to measure local variations in flatness of sheet material.

What is claimed is:

l. A method of measuring the flatness of rigid, moving sheet material, comprising supporting the sheet on two substantially horizontal supports spaced apart in the direction of movement of the sheet material, arranging above or below the moving sheet material a scale graduated to indicate the degree of flatness of the sheet material, and producing an ima e of the scale graduations by reflection m the upward y facing or downwardly facing surface of the sheet material in a region between said supports.

2. A method as claimed in claim 1, in which the scale is graduated directly in mon numbers.

3. A method as claimed in claim 1, in which the scale is graduated to indicate sheet material with a long center condition and sheet material with along edge condition.

4. A method of measuring the flatness of sheet metal strip as it is being produced in a rolling mill, comprising supporting the moving strip in a pair of spaced-apart supporting rollers having their axes of rotation substantially horizontal and disposed substantially at right angles to the direction of movement of the strip, arranging above or below the moving strip a scale graduated to indicate the degree of flatness of the strip, and producing an image of the scale graduations by reflection in the upwardly facing or downwardly facing surface of the strip in a region between said supporting rollers.

5. Means for measuring the flatness of sheet metal strip moving between two substantially horizontally disposed supporting rollers as it is being produced in a rolling mill, comprising a substantially rectilinear scale graduated in mon numbers for the strip, and a frame adapted to support the scale substantially horizontally at a predetermined distance above or below the moving strip in a direction substantially at right angles to the direction of movement of the strip.

6. Means as claimed in claim 5, in which the scale is formed along a generatrix ofa hollow drum.

7. Means as claimed in claim 6, in which the scale graduations are formed by holes formed through the drum, and in which a light source is arranged within the drum.

8. Means according to claim 6, in which the drum is provided with a plurality of scales each disposed along a different generatrix of the drum, and in which the drum is mounted for rotation about its longitudinal axis. 

1. A method of measuring the flatness of rigid, moving sheet material, comprising supporting the sheet on two substantially horizontal supports spaced apart in the direction of movement of the sheet material, arranging above or below the moving sheet material a scale graduated to indicate the degree of flatness of the sheet material, and producing an image of the scale graduations by reflection in the upwardly facing or downwardly facing surface of the sheet material in a region between said supports.
 2. A method as claimed in claim 1, in which the scale is graduated directly in mon numbers.
 3. A method as claimed in claim 1, in which the scale is graduated to indicate sheet material with a long center condition and sheet material with a long edge condition.
 4. A method of measuring the flatness of sheet metal strip as it is being produced in a rolling mill, comprising supporting the moving strip in a pair of spaced-apart supporting rollers having their axes of rotation substantially horizontal and disposed substantially at right angles to the direction of movement of the strip, arranging above or below the moving strip a scale graduated to indicate the degree of flatness of the strip, and producing an image of the scale graduations by reflection in the upwardly facing or downwardly facing surface of the strip in a region between said supporting rollers.
 5. Means for measuring the flatness of sheet metal strip moving between two substantially horizontally disposed supporting rollers as it is being produced in a rolling mill, comprising a substantially rectilinear scale graduated in mon numbers for the strip, and a frame adapted to support the scale substantially horizontally at a predetermined distance above or below the moving strip in a direction substantially at right angles to the direction of movement of the strip.
 6. Means as claimed in claim 5, in which the scale is formed along a generatrix of a hollow drum.
 7. Means as claimed in claim 6, in which the scale graduations are formed by holes formed through the drum, and in which a light source is arranged within the drum.
 8. Means according to claim 6, in which the drum is provided with a plurality of scales each disposed along a different generatrix of the drum, and in whIch the drum is mounted for rotation about its longitudinal axis. 